Microwave electronic devices, sometimes referred to as radio frequency (RF) devices, perform a number of extremely important functions such as in radars and high speed communications systems, etc. A number of physical structures such as waveguides and various types of amplifiers are used to direct and modify the electromagnetic RF signals that are typically within a range of around 0.3 GHz to above 300 GHz. Folded waveguides are devices that guide an RF signal along a meandering path to introduce a delay or a phase shift in the signal, sometimes needed in an amplifier. For example, a traveling wave tube (TWT) is a vacuum device that amplifies the gain, power or some other characteristic of an RF signal by causing an electron beam to interact with and transfer energy to the RF signal. The gain is typically increased when the axial velocity of the RF signal closely matches the axial velocity of the electron beam. A magnetic field may be used to steer and focus the electron beam into a straight and narrow line so that it doesn't directly touch the structure of the TWT. The folded waveguide may be used in the TWT to reduce the axial velocity of the RF signal so that it more nearly matches the velocity of the electron beam. The RF signal slows axially when it is forced to travel from side to side along the meandering path of the folded waveguide rather than just straight through the TWT alongside the electron beam. The folded waveguide thus delays the RF signal through the TWT, matching its axial velocity to that of the electron beam and maximizing the transfer of energy from the electron beam to the RF signal.
Folded waveguides can be difficult to manufacture because of the high speed of RF signals. The dimensions of microwave devices are often dictated by the ultra-small wavelength of the RF signal, and manufacturing a device with many direction changes and extremely close tolerances remains a challenge.